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General Information

Product Info

The MERIT DEM was developed by removing multiple error components (absolute bias, stripe noise, speckle noise, and tree height bias) from the existing spaceborne DEMs (SRTM3 v2.1 and AW3D-30m v1). It represents the terrain elevations at a 3sec resolution (~90m at the equator), and covers land areas between 90N-60S, referenced to EGM96 geoid. The data is freely available for research and education purpose.
Please e-mail to the developper (Dai Yamazaki: yamadai [at] rainbow.iis.u-tokyo.ac.jp ) to aquire the password for downloading. For commercial use, please also consult with the developer.

Data Summary

Spaceborne Digital Elevation Models (DEMs) are a fundamental input for many geoscience studies, but they still include non-negligible height errors. Here we introduce a high accuracy global DEM at 3 arcsecond resolution (~90 m at the equator) by eliminating major error components from existing DEMs (NASA SRTM3 DEM, JAXA AW3D DEM, Viewfinder Panoramas' DEM). We separated absolute bias, stripe noise, speckle noise and tree height bias using multiple satellite datasets and filtering techniques. After the error removal, land areas mapped with 2 m or better vertical accuracy were increased from 39% to 58%. Significant improvements were found in flat regions where height errors larger than topography variability, and landscapes such as river networks and hill-valley structures became clearly represented. We found the topography slope of previous DEMs was largely distorted in most of world major floodplains (e.g. Ganges, Nile, Niger, Mekong) and swamp forests (e.g. Amazon, Congo, Vasyugan). The newly developed DEM will enhance many geoscience applications which are terrain-dependent.
-- Description Paper in GRL

Data Source

MERIT DEM was developed by processing the following products as baseline data (all are freely available from their web page).
- NASA SRTM3 DEM v2.1: link to the SRTM webpage
- JAXA AW3D-30m DEM v1: link to the AW3D-30m webpage
- Viewfinder Panoramas' DEM link to the ViewfinderPanoramas webpage

In addition to the above baseline DEMs, below products were used as supplementary data:
- NASA-NSIDC ICESat/GLAS GLA14 data link to the NSIDC webpage
- U-Maryland Landsat forest cover data link to the Global Forest Change webpage
- NASA Global Forest Height Data link to NASA webpage
- JAMSTEC/U-Tokyo G3WBM water body data link to G3WBM webpage

GRW-LR

Close-up view of the MERIT DEM and the Original SRTM DEM, for the Mekong Delta and the Amazon Floodplain. Improvement by removing stripe noise, speckle noise, absolute bias, and tree height bias can be recognized.

Data Description

Data Format

The MERIT DEM is referenced to WGS84 and EGM96.
The data is prepared as 5 degree x 5 degree tiles (6000 pixel x 6000 pixel).
Filename represents the center of the lower left pixel of the data domain; e.g. the file "n30w120_dem.flt / n30w120_dem.tif" is for the DEM of the domain N30-N35, W120-W115. (more accurately, N29.99991667-N34.99991677,W120.00004167-W115.00004167)

The 5 deg tiles are compressed into 30 degree (lat) by 30 degree (lon) package.
Package name represents the lower left corner of the package domain; e.g. the package "dem_flt_n30w120.tar.gz" contains the files in the domain of N30-N60, W120-W090.

The data format is 'Fortran Direct Access Format' (i.e. ESRI 'FLT' raster format with the HDR file, GrADS binary with CTL file). Data is stored in 4-byte float, little endian.
GeoTiff file is also available

MERIT_tiles

Download

Current version is v1.0.1 [15 May, 2017]

UPDATE NOTE:
Bug fix on the geolocation tag in GeoTiff and EHdr metadata (v1.0 was half a pixel shifted). No change in the elevation data itself. [v1.0 -> v1.0.1] (28June,2017)
Improvement on surface elevations of large lakes above 60N (due to lake ice problem on AW3D) [v0.4 -> v1.0] (15May,2017)
Elevation of Grand Canyon, US (due to problem of SRTM3 elevations) [v0.4 -> v1.0] (15May,2017)
Tile package size was changed from 60deg*30deg to 30deg*30deg. (14June,2017)

NOTE: for users who have trouble in downloading large-size files, the direct link to 5deg*5deg tiles is also available: 5deg tile download page.

Terms and Conditions

Agreement to Terms and Conditions is required for using MERIT DEM.
Please e-mail to the developer to acquire password for downloading MERIT DEM. Please describe your name, research institute, and purpose of using MERIT DEM in the e-mail.

Data sharing policy

The data is freely available for research and education purpose. For commercial use, please consult with the developer (Dai Yamazaki).

Citation to the paper is adequate if you simply use the MERIT DEM. If you asked help for additional handling/editing of the dataset, or your research outcome highly depends on the product, the developer would request co-authorship.

[ Citation ]
Yamazaki D., D. Ikeshima, R. Tawatari, T. Yamaguchi, F. O'Loughlin, J.C. Neal, C.C. Sampson, S. Kanae & P.D. Bates
A high accuracy map of global terrain elevations
Geophysical Research Letters, vol.44, pp.5844-5853, 2017 doi: 10.1002/2017GL072874
-- Absstract in GRL

MERIT DEM (available at http://hydro.iis.u-tokyo.ac.jp/~yamadai/MERIT_DEM)

Sample Data (password not required)

Sample data for tiles n30w095 (N30-N35, W95-W90; Mississippi River) and n10e105 (N10-N15, E105-E110; Mekong River) is available without password. It contains both the new and original DEMs with a same data format.
Sample Data

ESRI EHdr format (password required)

N60-N90
dem_flt_n60w180.tar.gz ::: dem_flt_n60e000.tar.gz
dem_flt_n60w150.tar.gz ::: dem_flt_n60e030.tar.gz
dem_flt_n60w120.tar.gz ::: dem_flt_n60e060.tar.gz
dem_flt_n60w090.tar.gz ::: dem_flt_n60e090.tar.gz
dem_flt_n60w060.tar.gz ::: dem_flt_n60e120.tar.gz
dem_flt_n60w030.tar.gz ::: dem_flt_n60e150.tar.gz

N30-N60
dem_flt_n30w180.tar.gz ::: dem_flt_n30e000.tar.gz
dem_flt_n30w150.tar.gz ::: dem_flt_n30e030.tar.gz
dem_flt_n30w120.tar.gz ::: dem_flt_n30e060.tar.gz
dem_flt_n30w090.tar.gz ::: dem_flt_n30e090.tar.gz
dem_flt_n30w060.tar.gz ::: dem_flt_n30e120.tar.gz
dem_flt_n30w030.tar.gz ::: dem_flt_n30e150.tar.gz

N00-N30
dem_flt_n00w180.tar.gz ::: dem_flt_n00e000.tar.gz
n00w150 --no land data-- ::: dem_flt_n00e030.tar.gz
dem_flt_n00w120.tar.gz ::: dem_flt_n00e060.tar.gz
dem_flt_n00w090.tar.gz ::: dem_flt_n00e090.tar.gz
dem_flt_n00w060.tar.gz ::: dem_flt_n00e120.tar.gz
dem_flt_n00w030.tar.gz ::: dem_flt_n00e150.tar.gz

S30-N00
dem_flt_s30w180.tar.gz ::: dem_flt_s30e000.tar.gz
dem_flt_s30w150.tar.gz ::: dem_flt_s30e030.tar.gz
dem_flt_s30w120.tar.gz ::: dem_flt_s30e060.tar.gz
dem_flt_s30w090.tar.gz ::: dem_flt_s30e090.tar.gz
dem_flt_s30w060.tar.gz ::: dem_flt_s30e120.tar.gz
dem_flt_s30w030.tar.gz ::: dem_flt_s30e150.tar.gz

S60-S30
dem_flt_s60w180.tar.gz ::: dem_flt_s60e000.tar.gz
s60w150 --no land data-- ::: dem_flt_s60e030.tar.gz
s60w150 --no land data-- ::: dem_flt_s60e060.tar.gz
dem_flt_s60w090.tar.gz ::: dem_flt_s60e090.tar.gz
dem_flt_s60w060.tar.gz ::: dem_flt_s60e120.tar.gz
dem_flt_s60w030.tar.gz ::: dem_flt_s60e150.tar.gz

GeoTiff format (password required)

N60-N90
dem_tif_n60w180.tar.gz ::: dem_tif_n60e000.tar.gz
dem_tif_n60w150.tar.gz ::: dem_tif_n60e030.tar.gz
dem_tif_n60w120.tar.gz ::: dem_tif_n60e060.tar.gz
dem_tif_n60w090.tar.gz ::: dem_tif_n60e090.tar.gz
dem_tif_n60w060.tar.gz ::: dem_tif_n60e120.tar.gz
dem_tif_n60w030.tar.gz ::: dem_tif_n60e150.tar.gz

N30-N60
dem_tif_n30w180.tar.gz ::: dem_tif_n30e000.tar.gz
dem_tif_n30w150.tar.gz ::: dem_tif_n30e030.tar.gz
dem_tif_n30w120.tar.gz ::: dem_tif_n30e060.tar.gz
dem_tif_n30w090.tar.gz ::: dem_tif_n30e090.tar.gz
dem_tif_n30w060.tar.gz ::: dem_tif_n30e120.tar.gz
dem_tif_n30w030.tar.gz ::: dem_tif_n30e150.tar.gz

N00-N30
dem_tif_n00w180.tar.gz ::: dem_tif_n00e000.tar.gz
n00w150 --no land data-- ::: dem_tif_n00e030.tar.gz
dem_tif_n00w120.tar.gz ::: dem_tif_n00e060.tar.gz
dem_tif_n00w090.tar.gz ::: dem_tif_n00e090.tar.gz
dem_tif_n00w060.tar.gz ::: dem_tif_n00e120.tar.gz
dem_tif_n00w030.tar.gz ::: dem_tif_n00e150.tar.gz

S30-N00
dem_tif_s30w180.tar.gz ::: dem_tif_s30e000.tar.gz
dem_tif_s30w150.tar.gz ::: dem_tif_s30e030.tar.gz
dem_tif_s30w120.tar.gz ::: dem_tif_s30e060.tar.gz
dem_tif_s30w090.tar.gz ::: dem_tif_s30e090.tar.gz
dem_tif_s30w060.tar.gz ::: dem_tif_s30e120.tar.gz
dem_tif_s30w030.tar.gz ::: dem_tif_s30e150.tar.gz

S60-S30
dem_tif_s60w180.tar.gz ::: dem_tif_s60e000.tar.gz
s60w150 --no land data-- ::: dem_tif_s60e030.tar.gz
s60w150 --no land data-- ::: dem_tif_s60e060.tar.gz
dem_tif_s60w090.tar.gz ::: dem_tif_s60e090.tar.gz
dem_tif_s60w060.tar.gz ::: dem_tif_s60e120.tar.gz
dem_tif_s60w030.tar.gz ::: dem_tif_s60e150.tar.gz